Wake turbulence?

[Cymmon]

On a recent flight into Manila from Xiamen on a China Southern A320 we hit what I would call heavy turbulence.

The approach was normal, then turbulence kicked in, just (to me the usual), then suddenly a jolt and perceived "drop" in altitude. Not a bump, a drop. Then very quickly a very big sound of rushing wind.

The engines seemed to throttle back, then after 30-40 seconds spooled up again and we carried on a normal approach.

Sorry for my lack of professional words here, I'm a regular flyer, but not a pilot. I'm trying to avoid all the school, hospital type references, but just wondering if this was wake turbulence from the aircraft in front?

My main reference is the sharp drop and the sound of rushing wind that I've never heard before in all my years of flying.

Thanks.

[frequentflyer2]

Mrs FF and I were on an ERJ 145 when it got caught in wake turbulence approaching MAN. It was a lovely summer morning and we were over Stockport when the aircraft rolled violently to one side. It then righted itself before rolling violently to the opposite side. Full power was applied and the pilot abandoned the approach and climbed. He spoke to the cc member at the front of the aircraft who assured him no-one had been injured and then informed the passengers by intercom our flight had been caught in the wake vortex of a heavy aircraft. We went round and made a second normal approach and landing.

[PAXboy]

Cymmon Proper people will be along shortly, I'm sure. What you experienced may have been Wind Shear. However, on approach and departure, differing wind conditions tend not to arrive one at a time. If the weather is changing then you might expect several contrary wind events to happen at the same time.

One possible explanation of the 'wind rush' sound is that, if the external air pressure changed suddenly, it could affect the air conditioning system as well as any changes the flight deck made. I sit to be corrected.

[Cymmon]

Hi PAXboy, the wind I heard was definitely external. A whirling, swirling sound.

I've been through windshear before, but this was very different in feeling.

[wiggy]

Doubt you'd hear anything from a wake encounter (other than perhaps the contents of the galley hitting the floor)

You can get cabin/flight deck noise if you fly through heavy precipitation (e.g. Hail) and that may well come with associated turbulence. Other option would indeed be air conditioning noise as described by Paxboy, especially if there was a sudden reduction in power.

[PAXboy]

Interesting Cymmon, can't say I've heard that high a level of sound from outside before. Another thing about air-con is that, during time of high demand on the engines - takeoff- the flight deck will reduce or partially shut down some of the air-con packs so as to have maximum power available for any action they have to take. So they may also do that during turbulence.

[Cymmon]

That's why I posted, in the many flights, in the thousands, I've never heard a sound like that before. It was definitely outside, not any aircon or things like that.

The sound was unique to me. Just almost like a vortex sound.

Bearing in mind this is an approach to Manila in fairly poor weather, nothing spectacular, but not a nice clear day...

[Cymmon]

Can anyone else please comment on this?

It's just bugging me that I dint know what happened,but it was a very different event to what I'm used to.

[S.o.S.]

I started out by saying:
We have a long established convention in PPRuNe: 'Play the ball - not the Player'


I have now deleted posts that were unnecessary and rude and Yellow Cards have been issued.

It seems likely that the question may never have an answer but it IS an interesting question and it would be great if we can find an answer. If you don't have an answer - don't answer. Those who want a conversation and to swap information should stay, others can go to the Jet Blast forum to practise their skills. They will find the moderators there are not as lenient as I am.

[gusting_45]

Hi,

Can't say if the circumstances were the same, but what you heard and felt sounds quite similar to what I encountered some years ago.

We were operating a flight from STN TO VLC. The atmosphere was a bit unsettled and on one or two occasions whilst in the cruise through France there was a slight rushing noise associated with significant changes in wind speed and direction. Not a lot of turbulence though. However whilst over the Pyrenees we had a much more significant encounter with much more pronounced changes of wind speed and direction and a louder rushing noise. The turbulence was quite pronounced such that a few passengers and a number of crew were upended. Happily none injured though. The encounter from start to finish probably only lasted 10 to 15 seconds and was preceded and succeeded by almost entirely smooth flight conditions.

As a pilot of quite a few years, this encounter remains one of the few unexplained mysteries. The only conclusion that I came to was that the noise was due to sudden changes to the loading on the wing.

I know this doesn't provide much of an explanation, however, I would discount any air conditioning solutions as crew really should have better things to do than turn on/off air conditioning packs or selecting engine bleeds on/off etc whilst on an approach.

[Cymmon]

Gusting_45, Thank you for that answer.

That basically summed up what happened on my flight.
I was also in front of the wing, (not as far forward as yourself) but the rush of wind sound and perceived altitude drop was definitely disconcerting. The crew were given a warning and DID react accordingly.

So it looks like it was a definite change in wind speed/direction, which could be any of windshear, wake turbulence or just the weather. As I stated it was certainly not a clear , calm, sunny day on that approach to Manila.

Thank you very much for your informed answer. That is all I asked for. It never phases me, but I just like to have an idea, why, what, when and for....

Looking forward to my next flights, Man-Doh-Mnl to see the birth of my first child and to marry my girlfriend .

Easy or Ryan, or am I confused? :-)

Thank you.

[Piltdown Man]

Wave vortex encounters are generally very brief. Interesting, violent, unexpected, dangerous are all words that could be used to describe such events. But they are generally very short lived things because we don't like being there! But mishandled approaches, thermal disturbance, mountain wave, technical problems (pack or bleed failure) are all longer term events and could have given rise to what you were describing.

PM

[Cymmon]

Thanks for that, the encounter was a maximum of 10 seconds....

[Pontius Navigator]

Turbulence from a previous large aircraft is usually apparent when there is little wind to move the disturbed air mass.

Another more frightening reason for the noise might be the close proximity of another aircraft.

I recall once becoming aware of a gradual increase in external noise. We were flying at around 40,000 feet in light cirrus at night. Suddenly the penny dropped, we were catching up the aircraft in front.

[Hotel Tango]

Some 25 years ago or so I was flying on an B727 to Detroit when I heard an unusual rapidly approaching and loud sound. It lasted seconds and was gone just as rapidly. Speaking to the F/O after landing he told me that another B727 had crossed directly overhead us (with the required minimum seperation of 1000ft of course - we at FL280 and they at FL290). That sound was a weird experience at the time.

[Cymmon]

Thanks once again for those replies, it's slowly giving me an idea of what maybe happened on that approach.

[FlightDetent]

When I used to go planespotting, you could hear easily the wake vortices on a dry day below approach path close to the runway. I believe it is entirely possible to hear a vortex inside the cabin, especially if you happen to be flying through it!

regards, FD.